TEHRAN, YJC. -- Five world powers are urging Iran to heed demands aimed at easing fears that it might want nuclear arms.

The United States, Russia, China, Britain, France and Germany say it is "essential and urgent” that Iran reach an agreement with the International Atomic Energy Agency that will allow the IAEA to investigate suspicions Iran worked on such weapons.

The five say IAEA access to Parchin is particularly important. The agency has tried vainly over 18 months to visit the suspected site of weapons-related experiments.

They also said they are "deeply concerned” about Iran’s enriched uranium programme and a reactor that will produce plutonium when finished, in an address Wednesday to the IAEA’s 35-nation board. Both can be used to make nuclear weapons.